Background: underlay+overlay

A common process in biology is something called an “underlay” (or its cousin the overlay). This is a process of separating cells from other gunk by density. This is done like so: Say the cells are density x and the surrounding garbage is all significantly higher or lower density. by having two fluids sitting on top of each other and then centrifuging hard for a long time, the cells will float to the middle of the tube, where they can be collected. Setting this up is a tedious, time consuming and manual process that is prone to error. For an underlay, you first fill the tube halfway with fluid density $x - Δ$ , gently insert a pipette to the bottom of the tube, and sloooowly inject the fluid of density $x + Δ$ . You do the reverse with an overlay, which a lot of people prefer. $Δ$ is very small. Idk how small, but small. This seems to me to be a process that could be automated fairly easily. Some nice flow control on a pump and a barometer to sense fluid levels should be all that’s required I would think.

Valves and such

I have acquired a resin printer (elegoo mars) and so am now capable of printing airtight structures with tubes and such going through them. This should be perfect for the job. The first thing I did was print up a very simple manifold that directed the air around so I could either pump air in or out of a pipette. That looked like this: Which had the following circuit diagram: Where green are hoses and purple is the thing that I printed. That worked well, but had loads of hoses going all over the place. What I really want is a single block of printed stuff that I attach moving bits to that then does the job flawlessly. The first step in achieving this goal is to make some printable valves. Here is what I came up with: The air wants to flow from left to right from the red to the orange channel. But it can’t because the rubber sheet (light blue) is being pressed down over the junction by a solenoid (dark blue). In CAD it looks like this: